William w



seamed Nov. 15, 1932 Rel 18,652

UNITED sr 'rz p M 1 OFFICE,

wn'mnm w. SMITH, or IBUEFALO, new Yonx, assmnon To run now cnmncn. coltramr, or MI LAND,- MICHIGAN, a coupons-non or xrcnrem casrme BEADILY oxmrzmn Earns :6 Drawing. Original in.

This invention relates to thecasting of freely oxidizable metals such for example,

as magnesium and high magnesium alloys, and to the compositions for the forming of I molds for use in connection with the molding of such metals. d

The objects of this invention are to provide a method of casting freely oxidizable 'metals in such a manner as to prevent the metals from reacting with moisture contained in the mold; also to produce a molding composition which will form castings havin smooth surfaces free from sand holes, and w ich prevents the burning or oxidation of magnesium or other readly 'oxidizablemetals; .also to provide a composition of this kind which does not penetrate the castlng and which does not in any way change the appearance or composition of the metal; also to provide a composition of this kind which connection with molding of 'readilyoxidizable metals are replaced by. pulverized or finely divided carbon; Sandhas the disadvantage that it has a tendenc to penetrate thesurface of the casting an consequently roughens the. surface and forms sand holes therein.

Graphitediscolors the casting bydarkeningthe same, which renders the use of graphite objectionable. I have found that pulverized carbon does not have the objections of either sand or graphite and does not deteriorate with repeated use in molds and has no chemical reaction whatever with magnesium. Pulverized carbon may be used in various proportions from 50 to 90 per cent by volume.

My improved moldmg composition also in cludes magnesium oxide in varying proportions from 5 to 50 per cent. a

-Magnesium oxide can be either mixed into the molding composition or may also be used v for dusting on the surfaces of the mold with whichth'e molten metal contacts. The magnesium oxide may used repeatedly in the making of castings.

1,761,498, dated June 8', 1980, Serial No. 271,118, filed April 18, 1928. Application tor reissue filed April 4, 1932. Serial No. 803,195.

Powdered or finely divided soapstone is also added to the molding composition in varying proportions from approximately 2 to 15 per cent by volume. This material is chemically inert with reference to magnesium and other metals and can be readily freed from water and has the property of making the molding composition more or less adhesive and makes the composition pack,' so that the composition will retain the form or shape into which it is molded. Soapstone together with the light paraifin oil hereinafter referred to forms a bond or hinder between the carbon particles and consequently in case the composition is used for making comparative- 1y fiat castings or castings made from simple patterns, smaller percentages of soapstone can be used while inthe making of more complicated castings which require considerable draw, larger percentages of soapstone are requiredin order to moisten these three finely divided or pulverized materials to form a mass that can be molded, I employ a mineral oil of hght body. This oil is used in quantities suiiicient to moisten the material and enable the material to retain the form into which it is molded. A light bodied parafiin oil of specific gravity of about .875, a flash point of about 310? F., and a fire point of 355 F. has been successfully used in my improved .molding composition.

During the use of the mold some of this oil is evaporatedand when it is desired to again use'the remammg molding composition for making additional" castings, it is merely necessary to add suflicientoil to again moisten the material, the other ingredients of the molding composition remaining substantially unchanged during their use.

In accordance with my improved process of castin ized car mixed in the desired proportions and magnes1um. oxide may be added if desired. To

readily oxidizable metals, pulver-. on and powdered soapstone are these dry materials is added sufiicient of the light' bodied parafiin oil to moisten the mass 'so that the same can be molded. The material is then formedinto a mold in the usual manner as in the case of sand molds and magnesium oxide ma then be dusted on the portions of the mol with which the metal contacts.v The metal may then be poured into the mold. M In the case that magnesium oxidev is added to the molding composition, the dusting of, the mold with magnesium oxide may be omitted, but in many cases it is desirable to use magnesium oxide both in the composition and for covering the surfaces of the mold with which the metal contacts.

The composition described has the advantages that it is free from sand and that none of the materials used therein are hygroscopic.

The magnesium oxide is an important mgredient of this composition in that it prevents the magnesium from burning or oxidizing- Castings made by using my 1mproved molding composition are sand proof and without scale or rough surfaces and consequently can be made with greater accuracy magnesium oxide, powdered s'oa stone, and a light bodied mineral oil and having the surfaces of the mold which contact with the metal dusted with magnesium oxide.

6. The process of making castings of metals which are freely oxidizable, which consists of'pouring the metal in molten form into 'a mold containing powdered carbon and a temporary binder, and having magnesium oxide covering the surface of the mold with which the metal contacts. 7 l

Signed by me this 29th day of March, 1932.

WILLIAM W. SMITH.

by the use of this molding composition and the surfaces thereof are much smoother than castings made in sand molds so that the machining of castings made with my molding composition is greatly reduced. The oil used, being light bodied, does not form a per- 7 manent carbonvbond between the particles sists of pourin used in the mold, but volatilizes either entirely or partly when the metal is oured into the mold, so that the mixture 0 solids included in the compositionmay be repeatedly used in molding readily oxidizable metals, as-

is sand in the case of molding iron, brass I and other metals. More mineral oil is added as required, when the solids are again used for making a mold.

I claim as my invention 1. A mold containing pulverized carbon, pulverized soapstone, a temporary liquid binder and havmg magnesium oxide on the pao'ttsionsthereof with which the metal con- 2. mold made of about 50 to 90 per cent of pulverized carbon, from 2 to 15 per cent of powdered soapstone, and the balance of magnesium oxide and suflicient light bodied mineral oil to moisten the mixture,the surfaces of the mold which are to contact with the molten metal being dusted with magnesium oxide. 3 a

3. The process of making castings of metals which are freely oxidizable, which consists ofpouring the metal in molten form into a mold containing powdered carbon,

magnesium oxide and a temporary binder.

4. The process of making castings of metals which are freely oxidizable, which con;-

the metal in molten forminto a mold containing powdered carbon, magnesium oxide, powere soapstone, and a light bodied mineral oil. 5. The process of making castings of met- 'als which are freely oxidizable', which consists of pouring the metal in molten form into a mold containing powdered carbon, 

